(1) Field of the Invention
This invention relates to signal processing and in particular to dequantization of signals.
(2) Background Art
The process of quantization is understood broadly to include any process wherein a signal is divided by a quantization value in order to reduce the number of bits required to encode the signal. This is understood to cause the loss of a known amount of precision in order to achieve the reduction. It is well known to perform quantizing and dequantization operations in the field of compression and decompression of video and graphics signals. In the dequantization operation a quantized signal v is transformed into a dequantized signal d by a corresponding inverse operation.
In the field of video data processing it is known to perform dequantization using a quantization scaling factor Q as follows: EQU d=Q*(2*v+sign(v)) if (d is even)d=d-sign(d) Equations (1)
Unfortunately, the implementation of the dequantization operation of Equations (1) in software is fairly complex and computationally intensive. If this dequantization operation is performed by a processor it can not be performed with fewer than sixteen processor cycles in the prior art.
When performing a transform from a spatial domain representation of a video image to a frequency domain representation, the dequantization operation of Equations (1) must be performed once for every non-zero discrete cosine transform coefficient. In many typical video processing applications this may amount to performing these computationally intensive dequantization operations approximately once every sixteen pixels. Thus it would be advantageous to optimize the performance of this dequantization operation.